Reuse/copy pip code for VCS and download

[pombredanne]

pip is a good starting point as https://github.com/pypa/pip/blob/master/src/pip/_internal/download.py is a solid and reliable download utility tested with billions of downloads.

There are a few ways to handle this:

1. use https://github.com/sarugaku/pip-shims and reuse pip code
2. copy and fork pip code
3. vendor pip code

Note pip also handles VCS URLs
See https://github.com/pypa/pip/tree/master/src/pip/_internal/vcs
The download location specified in SPDX is mostly derived from the pip URLs https://github.com/spdx/spdx-spec/blob/db06dc81e525e08035af34117127742337e1f1b6/chapters/3-package-information.md#37-package-download-location-

pip does not handle ftp AFAIK

[TG1999]

Hi, can you tell me some steps that I should follow to solve this issue.

[TG1999]

From your description I understand that I should make a download.py file that should be like https://github.com/pypa/pip/blob/master/src/pip/_internal/download.py inside fetchcode. Are the steps correct?

[pombredanne]

Now that we have an API the next step is this ticket.

[TG1999]

https://github.com/pypa/pip/blob/master/src/pip/_internal/download.py this is missing now, I am not able to open it

[pombredanne]

It was there https://github.com/pypa/pip/blob/13ab7a2bce8fcde72b722cfc803d34671f1cd855/src/pip/_internal/download.py
but has now been exploded in this https://github.com/pypa/pip/tree/master/src/pip/_internal/network

This parts that deal with VCS is more stable
https://github.com/pypa/pip/tree/master/src/pip/_internal/vcs

In anycase we will have to fork as there is no stable code API in pip

[TG1999]

A little doubt, do we expect user to have installed git, mercurial or whichever VCS repo user wants to download.

[pombredanne]

@TG1999 yes. It would be nice if we cant use some library for Git, but reusing the command line should be simpler and this is how pip works and since this can be tricky code, best to reuse it

[pombredanne]

@pombredanne wrote

hey :) let me check in details what pip bit we could reuse
IMHO the vcs module is really worth it. It it a well tested command line wrapper for git/hg/svn etc... See https://github.com/pypa/pip/blob/e79fa0e8a249c3b3c6711e2ad85b0235a8a5d70a/src/pip/_internal/vcs/versioncontrol.py#L506 which is the entry point IMHO

@TG1999 replied

Okay I am getting you. So please correct my steps
First I should fork this pip repo
Then copy the code inside repo as it is in root directory
Then What should I do after that ?
Because the entry point versioncontrol.py needs some inner modules present inside pip so I have to copy the whole code then
Or only from the src/pip

[TG1999]

Hi, please can you explain me the steps :)

[pombredanne]

@TG1999 the things to do could be on of these:

1. reuse @techalchemy https://github.com/sarugaku/pip-shims
2. create a wrapper (likely reusing pip-shims) that would also vendor pip so we have this really reusable as a library
3. carefully extract the subset we care for (mostly the vcs module and its tests and deps) and just fork it

[pombredanne]

An alternative could be to look at https://github.com/juju/charm-helpers/tree/master/charmhelpers/fetch that has Git, bzr, http (and claims FTP support)

[TG1999]

Agreed @pombredanne I will send a PR by this weekend

[TG1999]

@pombredanne I think we can close this now :)